Simon Cowell claims he would "never work again" if people knew how "naughty" he was backstage.

Simon Cowell

Simon Cowell

The 56-year-old music mogul has revealed he and his fellow 'Britain's Got Talent' judges - Alesha Dixon, Amanda Holden and David Walliams - are terrible during audition breaks.

He said: "I'm not even going there, seriously. It's bad! Very naughty. We'd never work again if it went out. That's how we say goodbye to Got Talent - 'And this is what we didn't broadcast...'

Whilst Alesha told the Daily Mirror newspaper: "Simon is solely responsible for making us all act like 12-year-olds. We often say it's like being back at school because you act like silly school kids.

"We always say that if people could hear the conversations we have between us, or if we could air another show after dark with all the footage that doesn't go out then that would be hilarious."

Meanwhile, it was previously revealed that Simon has signed a deal for 'The X Factor' and 'Britain's Got Talent' to be broadcasted until 2019.

A source said at the time "This was always going to be a joint deal - Cowell, 'Britain's Got Talent' and 'The X Factor' come as a package.

"But a new three-year deal will be a huge relief to Cowell because it gives both shows a real sense of stability into the future. It will also end the constant rumours that 'The X Factor' is going to be axed."